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Watching a new ML320 teeter between two slippery mounds of red Alabama clay, dragging itself resolutely over the obstacles with any wheels--or wheel--that could find a scrap of traction, made it clear that we were observing an advance in the state of the art of sport-utility drive systems.

In fact, that first demonstration, held for worldwide members of the motoring press near the new Mercedes factory in Alabama, suggested that this fresh-sheet-of-paper SUV might just be the best in the business. And subsequent seat time has done little to dispel that notion.

Then again, best is a tricky word in the automotive lexicon. Comparative ratings of sport-utilities--or any other vehicles--are defined by their design and execution in terms of the perceived wants and needs of a particular market segment. But market segments don't buy vehicles. People do. And one buyer's best may have no appeal at all for the next.

Nevertheless, it seems to us that the new Mercedes M-Class makes a pretty good case for most sophisticated in the increasingly sophisticated world of sport-utilities, be they small, mid-size or full-size brute utes.

On the highway, the ML320 combines smooth ride quality with positive handling and surprisingly brisk acceleration for a vehicle that weighs more than two tons: 0-to-60 mph in 9 seconds.

On dirt or any slippery surface, its innovative full-time four-wheel-drive system makes the most of whatever traction is available, even if three of its four wheels can't get a grip.

Walkaround

With all this high-tech wizardry, plus extensive use of weight-saving materials, it's interesting that Mercedes chose traditional body-on-frame construction for its new wunderwagen.

Body-on-frame--the completed body is bolted to the rolling chassis as the final step in assembly--is still the preferred design for pickup trucks and most sport-utilities.

In unitbodies, an almost universal approach in passenger cars, the frame rails and bodywork are integrated.

Pros and cons: body-on-frame has a proven track record for its capacity to absorb punishment, while unitbodies save weight and are generally better at resisting squeaks and rattles.

Jeep has proved that unitbodies can handle the tortures of the trail, first with the Cherokee and later with the Grand Cherokee, and other manufacturers are following suit, notably Nissan and Toyota. Nevertheless, Mercedes--perhaps drawing on its experience with heavy trucks and military vehicles--chose the traditional approach, and the extra mass that goes with it.

Like the four-wheel-drive system, the ML320's aluminum 3.2-liter V6 engine--a production first for Mercedes--and computer-controlled 5-speed automatic transmission represent cutting-edge technology. It's basically the same combination used in the new Mercedes CLK coupe: With single overhead camshafts, three valves per cylinder, twin spark plugs, and individual ignition coils for each cylinder, the new Mercedes V6 is exceptionally light, efficient and powerful.

Peak horsepower--215--is very good for the size of the engine, but in a vehicle as heavy as the ML320 it's torque that counts. Torque is needed to get all that mass moving, torque is required for slogging up impossible slopes, torque is important for low-speed passing performance.

And torque what the new V6 delivers. At 233 pound-feet the Mercedes V6 is not quite as robust as the 4.3-liter pushrod V6 used in the Chevy Blazer, but it is superior to most engines of comparable displacement and it begins to assert itself almost at idle.

Incidentally, if the 3.2-liter V6 doesn't sound like it has enough suds for your needs, stand by: a 4.3-liter V8 version of the same engine will be coming along later this year in the appropriately named ML430.

As for style, it's mostly up front, topped off by that coveted three-pointed Mercedes star; the rear end isn't vastly dissimilar from other sport-utilities. And even though the production M-Class is far more traditional than the AAV concept vehicle unveiled at the 1994 Detroit show, the proportions are tidy and purposeful, with limited front and rear overhangs, a desirable attribute for off-road use.

Interior Features

Inside, the ML320 is pretty much what you'd expect of a Mercedes--well equipped, roomy, attractive and reasonably posh. The front bucket seats are nicely shaped, with a wide range of power adjustability, the rear row of seats consists of three individual buckets that can be folded forward separately to expand cargo space. Passive safety equipment includes front and side airbags, the latter mounted in the outboard edges of the front seats.

Considering its compact exterior, we were impressed with the amount of passenger space, as well as cargo capacity. However, we suspect that the optional third-row seat, which was not yet available during our various test drives, will be distinctly cramped. If you need eight-passenger seating in a mid-size SUV, the Dodge Durango is a better choice.

Our only other reservation regarding the interior was the quality of the interior materials, which seemed just a bit too commonplace in a Mercedes.

Driving Impressions

But that's where the similarity ends.

For one thing, the ML320 suspension is all independent, rather than employing traditional live axles at both ends, a plus in flexibility and in ride quality.

For another, instead of conventional locking differentials, which dictate uniform power delivery whether there's traction or not, the M-Class differentials are governed by Mercedes' 4-wheel electronic traction system (4ETS), originally introduced in Mercedes sedans and adapted for four-wheel drive. Electronically linked to the vehicle's antilock brake sensors, the system is designed to detect slippage at one or more wheels. When a wheel begins to spin, the system automatically applies braking to that wheel, thus sending engine torque only to the wheels that are still pulling.

In ordinary operation, torque is split evenly between front and rear wheels. But as long as one wheel has grip the ML320 can keep moving. This is particularly useful when only one wheel has firm contact with the earth. The only other SUV we've seen that's capable of this feat is the AM General Hummer, the warlord of sport-utilities. But even though the Hummer is still the ultimate off-roader, it's exactly as handy on the street as your average armored personnel carrier.

On the street, the ML320's mass is exceptionally well controlled. It changes directions well for a sport-utility vehicle--no drama, no peril--and the superb brake system delivers stopping distances worthy of a sport sedan. In fact, it's hard to believe this vehicle is as heavy as it is. It's even harder to believe it's a truck.

If there's any weak point on the dynamic scorecard it's the steering, which is short on feedback when the wheel is pointed straight ahead--no tactile information for the driver. But it doesn't take much steering input for the numbness to dissipate, and compared to most other sport-utilities, the ML320's steering is well above average. Call it a B on a report card otherwise festooned with As.

Final Word

Considering all its standard equipment, including the 4WD system, the ML320 is an exceptional SUV value. On the other hand, it's not cheap, with a $34,545 base price that's clearly luxury territory. Mercedes admits that it expects most new ML320s to roll out the showroom door for about $40,000 or more, because most owners will add options like power sunroofs, premium audio, and so on.

Even so, considering the level of refinement and technical sophistication that's included in the purchase price, including the innovative four-wheel drive system, we think this vehicle represents an exceptional buy. And we also think that this vehicle will have an impact out of proportion to its actual number.